Slotted component and method of manufacture thereof

ABSTRACT

A machine for machining slots within a bore of a sleeve includes a work holding device, and at least one cutting tool mounted on a cutting spindle. An axis of the cutting spindle is offset from and at substantially right angles to the axis of the sleeve. A device supports the cutting spindle for angular reciprocation to effect cutting strokes of the cutting tool relative to the surface of the bore.

This is a division of application Ser. No. 09/147,450 filed Mar. 17,1999 (which in turn is a National Stage Application of ParentApplication No. PCT/AU/97/00404) filed Jun. 25, 1997. The disclosure ofthe prior application(s) is hereby incorporated by reference herein inits entirety.

TECHNICAL FIELD

This invention relates to a method and apparatus for manufacturing aplurality of longitudinally extending slots in the bore of a component.One example of such a component is the sleeve element of an automotivepower steering rotary valve. More particularly the invention is directedtowards sleeve elements having varied slot configurations and themanufacture thereof.

BACKGROUND ART

The prior art most closely related to that of the present invention isthat covered by U.S. Pat. No. 5,328,309 (Bishop et al), U.S. Pat. No.5,292,214 (Bishop et al) and U.S. Pat. No. 5,390,408 (Bishop et al).These prior art references relate to “slotting machines” which machinethe slots in the bore of power steering valve sleeves. The design ofthese machines calls for each of the slots to be scooped out of the boreof a turned blank by a finger-like cutting tool mounted on a cuttingspindle which angularly reciprocates about an axis in a series ofprogressively deeper cutting and return strokes so forming a (usually)closed chamber, or hydraulic port, which is arcuate in longitudinalsection. The sleeve is held in a work holding collet, in turn mounted ina work holding spindle, having a rotational axis perpendicular to andoffset with respect to the cutting spindle axis. By accurately indexingthe work holding spindle upon completion of each slot, the requirednumber of slots are precisely machined in the sleeve, usually 4, 6 or 8slots for most automotive applications.

Such prior art slotting machines have always been arranged to form eachslot longitudinally in the bore surface, which is at the time of cuttingfurthest from the cutting spindle axis. In view of this and havingregard to the arcuate path of the cutting tool during each cuttingstroke, the slot has necessarily had a concave floor. This has limitedthe nature and configuration of the slots that have been able to beformed. The concave slots typically used have been blind-ended, but insome designs the concave slots exit from either or both axialextremities of the sleeve bore surface to provide for oil return fromthe sleeve.

It has been found that the aforesaid limitations on slot configurationhave imposed limitations on design of steering gear valves and an objectof the invention is to alleviate that situation.

SUMMARY OF INVENTION

In a first aspect the present invention is a machine for machining slotslongitudinally disposed within the bore of a sleeve, comprising a workholding device for holding said sleeve, at least one cutting toolmounted on a cutting spindle, the axis of said cutting spindle beingoffset from and substantially at right angles to the axis of saidsleeve, means of supporting said cutting spindle for angularreciprocation to effect cutting strokes of said tool relative to thesurface of said bore, infeed means to permit said cutting tool toexecute a succession of progressively deeper cuts in relation to saidbore of the sleeve, characterised in that when said cutting tool iscutting at least one of said slots, the cutting tool engages the surfaceof the bore at a location substantially closest to said axis of thecutting spindle.

Preferably the cutting operation takes place in a substantiallydiametral plane and the location closest to said axis of the cuttingspindle therefore lies in this substantially diametral plane. Preferablythe cutting tool is adapted to effect a convex path with respect to thesurface of the bore which it is engaging.

In a second aspect the present invention is a machine for machiningslots longitudinally disposed within the bore of a sleeve, comprising awork holding device for holding said sleeve, at least one tool headcarrying cutting means, said tool head mounted on or integral with acutting spindle, the axis of said cutting spindle being offset from andsubstantially at right angles to the axis of said sleeve, means ofsupporting said cutting spindle for angular reciprocation to effectcutting strokes of said cutting means relative to the surface of saidbore, infeed means to permit said cutting means to execute a successionof progressively deeper cuts in relation to said bore of the sleeve,characterised in that said cutting means comprises of two or moreindependent cutting tools.

Preferably in a first embodiment at least one of the cutting tools isadapted to effect a convex path with respect to the surface of the borewhich it is engaging.

Preferably in a second embodiment at least one of the cutting tools isadapted to effect a concave path with respect to the surface of the borewhich it is engaging.

In a third aspect the present invention is a one piece sleeve for arotary valve, the sleeve comprising an array of communication slotsformed in the bore of the sleeve, characterised in that at least aportion of the floor of one of said slots is convex.

Preferably in one embodiment the slot having a convex floor portion is areturn slot which extends longitudinally to at least one axial extremityof said bore surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example withreference to the accompanying drawings in which:

FIG. 1 is a sectioned perspective view of a slotting machine inaccordance with one embodiment of the present invention.

FIG. 2 is an elevational view of the tool head and cutting means of theembodiment shown in FIG. 1.

FIG. 3 is a partial vertical cross-section of a sleeve in a diametralplane with a blind-ended slot shown in relation to a cutting tool.

FIG. 4 is a partial vertical cross-section of a sleeve in a diametralplane with a convex slot portion shown in relation to a cutting tool.

FIG. 5 is an elevational view of a second embodiment of tool head andcutting means.

FIG. 6 is an elevational view of a third embodiment of tool head andcutting means.

FIGS. 7(a) to 7(e) show five sleeves with various slot configurations.

MODE OF CARRYING OUT INVENTION

FIG. 1 shows a slotting machine which holds sleeve 1 in collet 2 of workholding spindle 3 which is mounted for both rotation and axial slidingin machine base 4. A tool head 5 extends from, and in this embodimentintegral with, cutting spindle 7. Cutting means comprises cutting toolholders 100 and 101, respectively incorporating arms (or finger-likeprojections) 6 and 8, mounted to tool head 5. Arms 6 and 8 of toolholders 100 and 101 provide mounting for cutting tools 9 and 11respectively. Cutting spindle 7 oscillates angularly through an angle ofapproximately 45 degrees and cutting tools 9 and 11 are shown in theiruppermost position. Cutting spindle 7 is journalled for rotation aboutan axis 10 within spindle carrier 12 which is itself journalled about anaxis 13 in cutting capsule 14.

During the cutting operation only one of cutting tools 9 and 11 is usedat any one time, and the reciprocation of cutting spindle 7 about axis10 imparts an arcuate cutting stroke to the cutting tool being used,whilst oscillation of spindle carrier 12 imparts the necessaryretraction motion at the end of the cutting stroke.

The cam drive arrangement for imparting reciprocating motion to cuttingtools 9 and 11, the former which is housed within cutting capsule 14, isnot described herein as it is fully covered in U.S. Pat. No. 5,292,214(Bishop et al). The infeed mechanism may be of a mechanical cam driventype as described in the above referenced prior art or of a suitablenumerically controlled servo-drive mechanism, adapted to impart relativelinear horizontal motion between the cutting capsule 14 and the sleeve,thereby providing a means for infeeding one of the cutting tools duringa cutting operation.

The work holding spindle is also adapted for axial (vertical) linearmovement which may in operation be similar to that described in theabove referenced prior art U.S. Pat. No. 5,328,309 (Bishop et al), oralternatively by a suitable numerically controlled servo-drive means.This allows for the sleeve to axially clear the cutting tool. However,in another not shown embodiment the relative vertical linear movementbetween the work holding spindle and the cutting tool may be achieved byproviding a vertically movable cutting capsule.

FIG. 2 shows an elevational view in isolation of tool head 5 and cuttingtools 9 and 11, mounted on arms 6 and 8 of cutting tool holders 100 and101 respectively. Whilst in this embodiment cutting tool holders 100 and101 are each independent from one another and may each be separatelyremovably attached to tool head 5, it should be readily understood thatcutting tool holders 100 and 101 may be formed as a single component.

FIG. 3 shows sleeve 1 in its relation to a cutting tool 9 mounted on arm6 of toolholder 100, when cutting a blind-ended concave arcuate slot 15of the known type in bore 16. The angular reciprocation of the cuttingtool 9 is in a substantially diametral plane of bore 16 (ie in the planeof the section) and engages surface 17 of bore 16 in the diametral planefurthest away from cutting spindle axis 10. In such an arrangementcutting tip 18 of cutting tool 9 projects outwardly away from tool head5.

As the cutting capsule 14 is linearly (horizontally) movable withrespect to the tool head 5 and work holding spindle can be moved axially(vertically), sleeve 1 s able to be repositioned such that cutting tool11 may be utilised to cut a slot, or a portion of a slot, into anotherportion of surface 17 of bore 16.

FIG. 4 shows sleeve 1 in its relation to cutting tool 11 mounted on arm8 of cutting tool holder 101. The angular reciprocation of cutting tool11 is again in a substantially diametral plane of bore 16 and engagessurface 19 of bore 16 in the diametral plane closest to the cuttingspindle axis 10. Cutting tip 20 of cutting tool 11 projects inwardlytowards tool head 5. Such an arrangement allows for slot floors orportions of slot floors to be cut which are convex rather than concaveas at 102. Use of slot floors with convex portions will be laterdescribed and shown in FIGS. 7(b)-7(e).

Whilst the first embodiment of tool head 5 shown in FIG. 2 utilisesfinger-like cutting tool holders 100 and 101 which are able to cutconcave and convex slot portions respectively, it is possible in asecond embodiment (as shown in FIG. 5), to have two finger-like cuttingtool holders 103 and 104, both of which are for cutting slots withconcave floor portions. Such an embodiment could be used for machiningslots of two different widths on a sleeve in a single machine as shownin FIG. 1, by using different width cutting tips on cutting tools 109and 111.

In a third embodiment as shown in FIG. 6 two finger-like cutting toolholders 105 and 106 are both arranged for cutting slots with convexfloor portions. Again, such an embodiment could be used for machiningslots of two different widths on a sleeve in a single machine as shownin FIG. 1, by using different width cutting tips on cutting tools 107and 108.

Now referring to FIGS. 7(a) to 7(e), five different embodiments of slots21(a) to 21(e) are shown in sleeves 1(a) to 1(e) respectively. Forpurposes of clarity outside features of the sleeve have been omitted andthe dimensions appropriately altered. Also for ease of reference onlyone slot is shown in each sleeve. All five slot embodiments can bemachined on the machine of the first embodiment of the presentinvention.

FIG. 7(a) depicts sleeve 1(a) with blind-ended arcuate slot 21(a) whichhas a concave floor. This slot is similar to slot 15 shown in FIG. 3 andmay preferably be used as an inlet slot on the sleeve. Slot 21(a) is cutin a conventional manner discussed earlier on with reference to thetooling arrangement shown in FIG. 3, where angular reciprocation of thecutting tool 9 is in a diametral plane of bore 16 and engages surface17(a) of bore 16(a) in the diametral plane furthest away from thecutting spindle axis 10.

FIG. 7(b) depicts sleeve 1(b) with arcuate slot 21(b) which has a convexfloor and is open ended at both axial extremities of surface 17(b) ofbore 16(b) of sleeve 1(b). This slot may preferably be used as a returnslot on the sleeve. Slot 21(b) is cut in the manner discussed earlier onwith reference to the tooling arrangement shown in FIG. 4, where angularreciprocation of cutting tool 11 is in a diametral plane of bore 16(b)and engages surface 17(b) of bore 16(b) in the diametral plane closestto cutting spindle axis 10.

FIG. 7(c) depicts sleeve 1(c) with slot 21(c) having a slot comprisingthree distinct arcuate slot portions and is open ended at both axialextremities of surface 17(c) of bore 16(c) of sleeve 1(c). The centralslot portion has a concave floor, whilst the two outer arcuate slotportions have convex floors. This slot may also preferably be used as areturn slot on the sleeve. Slot 21(c) is machined by cutting the centralconcave portion of the slot by the tooling arrangement shown in FIG. 3,whilst the two outer convex portions may be machined by the toolingarrangement of FIG. 4. As the machine of the first embodiment has adouble headed tool adapted to cut both concave and convex portions, boththe convex and concave portions of slot 21(c) may be cut on the samemachine.

FIG. 7(d) depicts sleeve 1(d) with slot 21(d) which is open ended atboth axial extremities of surface 17(d) of bore 16(d) of sleeve 1(d).The central floor portion of slot 21(d) is substantially flat, whilstthe two outer arcuate slot portions have convex floors. This slot mayalso preferably be used as a return slot on the sleeve. The two outerarcuate slot portions may be cut in the manner discussed earlier on withreference to the tooling arrangement shown in FIG. 4. The substantiallyflat central portion of slot 21(d) may alternatively be convex with asubstantially large arc radius.

FIG. 7(e) depicts sleeve 1(e) with sleeve 21(e) having two convex slotportions, at opposed axial extremities of surface 17(e) of bore 16(e) ofsleeve 1(e). The two convex slot portions may be cut in the mannerdiscussed earlier on with reference to the tooling arrangement shown inFIG. 4.

The slots shown in FIGS. 7(b), 7(c), 7(d) and 7(e), as well as other notshown slot configurations utilising convex slot floor portions, aresuitable for use as return slots on sleeves for use with valvesdisclosed in our International Patent Application PCT/AU96/00266entitled “Rotary Valve for Power Steering Gear” and International PatentApplication PCT/AU96/00267 entitled “Power Steering Gear Valve” thedisclosure of which is incorporated herein by reference.

It will be recognised by persons skilled in the art that numerousvariations and modifications may be made to the invention withoutdeparting from the spirit and scope of the invention.

What is claimed:
 1. A machine for machining slots longitudinallydisposed within a bore of a sleeve, comprising a work holding device forholding said sleeve, at least one tool head carrying cutting means, saidtool head mounted on or integral with a cutting spindle, an axis of saidcutting spindle being offset from and substantially at right angles toan axis of said sleeve, means supporting said cutting spindle forangular reciprocation to effect cutting strokes of said cutting meansrelative to the surface of said bore, infeed means to permit saidcutting means to execute a succession of progressively deeper cuts inrelation to said bore of the sleeve, characterized in that said cuttingmeans comprises two finger-like cutting tool holders, each of whichcarries at least one cutting tool, and at least one cutting tool carriedby one of the two finger-like cutting tool holders has a cutting tip ofdifferent width to that of a cutting tip on the at least one cuttingtool carried by the other finger-like cutting tool holder.
 2. A machineas claimed in claim 1, wherein at least one of said two finger-likecutting tool holders and their respective cutting tools is adapted toeffect a convex path with respect to the surface of the bore which it isengaging.
 3. A machine as claimed in claim 1, wherein at least one ofsaid two finger-like cutting tool holders and their respective cuttingtools is adapted to effect a concave path with respect to the surface ofthe bore which it is engaging.